The present invention relates in general to rectifier circuits and, more particularly, to a rectifier circuit having first and second inputs interchangeably connected to first and second conductors.
Automobile manufacturers regularly include airbags as standard equipment in their vehicles to comply with federal regulations. Sensors placed at strategic locations in the vehicle detect a sudden deceleration or acceleration incident to a collision and provide an electrical signal to a distributed airbag firing system. Upon receiving the sensor signal indicating the sudden deceleration, an airbag controller sends a firing signal to a squib driver circuit. The squib driver circuit is electrically connected to a squib, which is a detonation wire or device used to ignite an explosive charge. There is one squib physically attached to each airbag. When enabled by the firing signal, the squib driver circuit sources a current through the squib to fire the explosive charge. The explosive charge releases a gas that inflates the airbag to protect the occupants of the vehicle during the impact.
The airbag and squib are physically located to protect the occupants, for example, in the steering column, the passenger dashboard, door panels, etc. The sensors are typically located near the points of highest probability of impact generally around the perimeter of the vehicle, e.g. side doors, and front and rear bumpers. The controller module is centrally located, for example, toward the rear of the engine compartment or behind the instrument panel. An electrical wiring harness interconnects the sensors, airbag controller, drivers, and squibs.
The squib driver circuits have first and second inputs electrically connected to the wiring harness to receive the command signal and energy to detonate the squib. The electrical connection is typically a two-wire contact to twisted pair conductors. In the prior art, it is important to make the correct polarity connection for proper operation of the squib driver. If the two-wire connection is reversed from its intended design, the squib firing system may not operate or produce undesired results.
Some prior art distributed firing systems have attempted to color code or mechanically key the two-wire connection terminals to reduce the possibility of incorrect connection. However, such solutions are more expensive to manufacture and still prone to human error. An airbag firing system is an important safety and liability issue and should be made as fail-safe as possible.
Also, because there is the possibility that one of the wires could be accidentally shorted to either vehicle supply (battery) or ground potential, it would be of benefit to be able to continue use the non-shorted wire for signaling. This requires that the system be able to receive signals when the applied polarity is the reverse of that used for normal operation.
Hence, a need exists to simplify and make fail-safe the two-wire connection of the squib driver to a wiring harness of a distributed airbag firing system.